1. Field of the Invention
The present invention relates to a vulcanized sheet comprising annular rubber articles such as bearing seals, a method of and an apparatus for separating the articles from the vulcanized sheet.
2. Prior Art
Each of the prior art rubber articles of this kind consists of a rubber ring reinforced with a metal ring secured therein. The rubber ring is made of an elastomer such as a synthetic rubber. The annular rubber articles are obtained by separation from a vulcanized sheet. Typically, the sheet is an integrally rubber sheet provided by the reinforcing metal rings into the elastomer by vulcanizing compression molding.
An example of the vulcanized sheet `S` shown in FIG. 10 comprises annular articles `P` arranged in rows and columns. An outer waste 1 surrounds each article `P`, and an inner waste 7 is enclosed therewith. Thus, the annular article `P` is integral with both the areas 1 and 7. FIG. 11 shows that the outer waste 1 consists of an external flash 3, an outermost thin and annular zone 4 and a body 5 of the sheet. This body 5 surrounds the annular zone 4, and an outer break line 2 is a boundary formed between the external flash 3 and an outer periphery of the annular article `P`. The zone 4 formed as a thin bottom of an annular groove is a zone which has prevented a molding pressure from escaping during vulcanization of the sheet. On the other hand, an inner break line 6 intervenes between the annular article `P` and the inner waste 7.
It has however been inefficient for any worker to manually tear the annular articles `P` one by one from the vulcanized sheet `S`. It is another problem that some of those manually separated articles possibly have their metal rings bent, thereby causing deformation of said articles. The hand of the worker likely soils the annular articles when he tears them off the sheet, further lowering the quality of those articles.
The extremely thin zone 4 surrounding the external flash 3 is too weak to protect each annular article `P` from an unintended slipping off. Some annular articles `P` will possibly be severed from the vulcanized sheet `S`, when the sheet is removed from a mold or is transported. It is a matter of course that such a loss lowers the yield of annular articles per sheet.
Certain apparatuses have recently been proposed so that the annular articles could automatically be torn off the vulcanized sheet, as disclosed for example in the Japanese Patent Publication No. 60-18525 or in the Unexamined Patent Publication No. 57-11038.
The apparatuses comprise each a punching device, a blanking device and a transporting device. The vulcanized sheet `S` will be carried by and along the transporting device so that the sheet's region where one of annular articles `P` is formed does take a correct position on the punching device. As the phantom lines in FIG. 11 indicate, a die 8 of this punching device will support the lower face of the article `P` when a punch 9 strikes the upper face of said article. After the inner waste 7 is thus removed, the region advances to the blanking device where the external flash 3 is supported by a similar die when another punch strikes the article `P` out of said sheet.
Even if any of the extremely thin zones 4 in the vulcanized sheet `S` is damaged to a slight extent that the annular article `P` would not slip off, this article may however be offset relative to the surface of said sheet. The shearing die and punch included for example in the punching device for removing the inner wastes 7 will thus fail to exactly cut the necessary portions. The cutting along the inner break line 6 will not be assured for that displaced article `P`, but a portion thereof or of the inner waste 7 adjacent to the break line may be cut. The annular articles having their portions erroneously cut away or having unremoved flashes do not qualify as acceptable good products.
Such a poor stability in position of the annular articles `P` will cause a more serious problem in a case wherein one punching or blanking operation separates at once a plurality of said articles from one vulcanized sheet. There has been a possibility that the punch could not sever any articles at all, thus lowering productivity. In order to avoid those troubles, extraordinarily accurate and complicated parts and structures have been necessary for the punches and dies to correct the position of each annular article.